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Thursday, November 17, 2005

SAP system landscape – basic idea for functional consultants

As we all know SAP works on client server architecture. The term client/server was first used in the 1980s in reference to personal computers (PCs) on a network. The actual client/server model started gaining acceptance in the late 1980s. The client/server software architecture is a versatile, message-based and modular infrastructure that is intended to improve usability, flexibility, interoperability, and scalability as compared to centralized, mainframe, time sharing computing.

I’ll explain the client server model using a small example. I’m sure that all of us have used Microsoft outlook to send and receive mails to our buddies. To send a mail we open the Microsoft outlook on our pc, type the new mail and press the send button. Here the Microsoft outlook acts as a client. Once we pressed the button outlook connects to the exchange server which will receive the request from the client and send the mail for you. Here the microsoft outlook as a client sends the request to the exchange server. server receives the request and process the tasks.

When the client and server programs both run on the same computer, the configuration is referred to as single-tier client/server. (A tier is the boundary between two computers.) When they run on different computers, the configuration is referred to as two-tier client/server.
A program can function as both a client and a server if it both requests information and replies to requests. When you have three programs in communication, the configuration is called three-tier client/server.

The main advantage of the software of this nature is that it can be fine tuned to give maximum performance for the given scenario. The client/server configuration enables the MySAP ERP system to spread its load across multiple computers. This provides the customer with the ability to scale the processing power of the system up or down by simply adding another computer to an existing configuration, instead of replacing a single computer that performs all of the processing, such as that which occurs in the mainframe world.

The main software components on a SAP system can be categorized as follows.
1.Presentation server
2.Application server
3.Database server

Presentation server

Presentation server is nothing but the laptop or PC which has sapgui.exe that you use to log into SAP system.

Application server

An application server is a set of executables that collectively interpret the ABAP/4 programs and manage the input and output for them. Application severs act like a mediators between the presentation server and the database sever. Application sever receives the requests from the presentation sever and process them on its work processes. I’ll talk about the work processes in details later on this blog. The important fact that I want to share with you is that the ABAP programs are processed by ‘Software processors’ and not directly by the CPU. I’ll discuss about the components of an Application sever later on this Blog too.

Database server

The database server is a set of executables that accept database requests from the application server. Database server will pass the requests to the RDBMS that has been used. As you should know SAP supports Database management systems from various vendors such as Microsoft SQL server, Oracle, Informix and Sybase etc. The RDBMS sends the data back to the database server, which then passes the information back to the application server. The application server in turn passes that information to the ABAP/4 program.

Some technical terms that useful to functional consultants

I think it’s appropriate to tell you the meaning for some terms used by technical consultants. If you hear a word MySAP ERP system or R/3 system, it means an implementation with one database. In other words, the implementation that you did for company A with one database as the backend is one system and the implementation at company B is another system

Another frequently used word is ‘Instance’ this simply means the application server. If your technical consultant buddy says we have one instance which means we have one application server. If he says five instances which mean five application servers are running on the environment. For example HP runs around 70 instances or application servers to manage its global transactions.

Different types of configurations

As we have seen above SAP is a client server based system which gives us enormous flexibility to configure the system to suit our environment. Presentation server, Application server and Database server can be put at different possible positions to get the maximum throughput from the system, which means there are virtually unlimited configuration possibilities.

1. SAP three-tier client/server configuration: the presentation servers, applications servers, and database server all run on separate machines. This is the most common configuration for large systems, and is common in production. As well as you can have multiple applications and database servers to share the work load.

2. SAP distribution presentation configuration: the application and database servers are combined on one computer and the presentation servers run separately. This is used for smaller systems, and is often seen on a development system.

3. SAP two-tier client/server configuration: the presentation and application servers are combined and the database server is separate. This configuration is used in conjunction with other application servers. It is used for a batch server when the batch is segregated from the online servers. A SAPGUI is installed on it to provide local control.

4. SAP central configuration: all servers are combined onto a single machine. This is rarely seen because it describes a standalone R/3 system with only a single user. I don’t think anyone will buy SAP with millions of dollars to install it on their PC :)

SAP is much more flexible than any other traditional ERP systems. It’s the duty of the technical and functional consultants to sit together to draft a technical system blueprint to maximize the performance of the SAP. As well as we should also consider the budget and hardware limitations when drafting a technical landscape.

I hope this article gave you a better understanding about the SAP technical landscape. Please feel free to send me a comment about this article by clicking on the ‘Comments’ button.


Anonymous said...

Very helpful article. I shall be glad to read more on how configurations affect performance.

Vijay Kumar said...

what is sap landscap

Anonymous said...

Very good article i have 4 years working with SAP and there are things that i did not know until now!!Thanks